Intensity control



Aug. 25,1931. o. voN BRONK E1' AL 1,820,335

I INTENSITY CONTROL Filed Aug. 6, 192'?` L-B AT RNEY Patented Aug. 25,1931 UNITED STATES PAfria-N'i- OFFICE orfio vou BRONK AND HANS mirror,onisnnmn enniwmivxnssienoas ToGEsELL- SCHAFT FUR DRAHTLDSE TELEGRAPHIEM. OF BEAR-LIN, IGrillillVlIANY, A COR? PORATION 0F GERMANY Iiv'rnnsifryooNTRoL Application filed August `6, 1927, Serial No. 211,084,211141 inGermany August 9, 1926'. I

Intensity variations or {iuctuations due to atmospheric conditions arerathercommon in Wireless telcgraphy. While vsuch fluctuations in readingtelegiaphy signals and in telephony and also in high-speedvreceptionwith recorder devices still allow Ofcomapparently unavoidable even byrepetitions of the massage or text.

The present invention discloses ways and means whereby the influences ofsuch liuctnations upon the quality vofthe pictures can be eliminated orat least greatly diminished. Fundamentally speaking, the inventionconsists in that in a system for transmitting and receivingT pictures byradio, orV even land line, the receiver or the picture, reproducingapparatus is given a changing' sensitiveness, the latter being adjustedin accordance with the prevailing intensity or volume of reception.Hence, if reception is strong, the sensitivity must be made small, whilethe sensitivity must be great whenever tlie incoming signals are Weak. yThis can be accomplished, for example,l by providing a receiverarrangement with an integrating action during a period which is long fcompared with the radio frequencycperiod or picture-element period(fractions of a' second), for example, a simple rectifier withcollecting condenser produces a direct current whose strength varies inconformity with the volume of reception, saidv direct current altering,for instance, in the shape of a grid potential, the sensitiveness of thepicture reproducing apparatus in the desired manner. Since the fading orinten'sityuctnations are generallyof a period amounting to severalseconds, such an integrating device of low inertia is capable ofkcompensating 'a large part of the intensity fluctuations.

Instead rent in an integrating manner from part-of the picture, thefollowing method could also be used :l ,f j

The picture is provided marginally with of deriving the regulating cur-rla distinct or separate strip of medium blackness, consisting, forinstance, of a shading as illustrated vby-portion S ofthe accompanyingdrawing. If, then, Zisthe direc-.- tion ofthe lines in the 'transmissionofthe picture, for, each line, during a certain fraction `of the time,the mean transingS will be present. More particularly speaking, thesaidstrip S may be used for the purposeofadjusting the Asensitiveness of"the apparatus for the next line inthedesii'ed manner.- Y

By the accompanying drawingswe have shown by Fig. 1 one form which ourinvention may assume, and by Fig. 2 a modified form of the inventionillustrating ka different volume control system.V It: is to theproduced'light may be directed through lenses ,or any other preferredmeans to Vinf be understood,(however, that such-forms FasV areillustrated'are purely by way of-example, and we believe ourselves to belimited' onlyin so .far as is necessary from thel 'mission intensity-Whicli is produced byV shadfluence a light sensitiver stripI Bon areceiv- Ving drum B. VThe receiving drumB is mounted upon'a shaft Cv andis:turned in 'any preferred mannerby a motor or other means of knownarrangement (not shown).

The movement of the light source M is likewise accomplished by means ofthe same motor that rotates the drum B and` through a gear mechanismVthe motork is adapted `to move thelight source M back and yforth upon aguide strip D ata speedwliich will be in` ysynchronisni withl that of asimilar light pick-up mechanism at the transmitting sta-y tion. As thelight source M moves back and-7 forth upon the guide strip D, uponreaching the end of each stroke means is preferably provided foradvancing the drum B a small fraction of an inch for recording the nextband of the picture on the light sensitive strip B. In the preferredembodiment of our invention the light sensitive strip B is provided atone edge (or even at beth edges) with an area or strip of darkened orshaded material S of which the intensity with which the light fromsource M for a given light intensity at the transmitter should shinethrough has been determined, since, at the transmitter a shaded strip orarea of like intensity to iniiuence a light sensitive means controllingthe transmitted. energy is provided.

At the same time that the light source M has been moved so that it isabove the darka cned strip S of the light sensitive film B,

- tensity of light from source M to produce the predetermined amount ofillumination upon the photo cell P is unobtainable and means must besupplied to increase the sensitivity of the system to produce a finishedpicture of even light distribution. Therefore, a standard of lightintensity M which. is the same as that which is passed through a likestrip S at the transmitter to influence the photo cell or" thetransmitter has been provided, and each time that the light source M isadvanced to reach the portion designated E of the guide strip D, aswitch J is closed. The closing of switch J lights the source M by meansof a battery L. The switch J includes a conducting strip E which hasbeen made a portion of the guide strip D and a conducting strip made apart oic the portion M including the light source. The circuit for thelight source M is closed through parts E, K and the bottom contact ofthe switch J.

Light shining from the light source M is carried through a screen S ofthe same darkness as the screened or shaded portion S which has been.made a part of the light sensitive film B. The light from M by means oflenses or other instrumentalities is directed to a photo cell P and bywhich means a current is caused to fiow owing to the fact that the lightchanges the resistance properties of the photo cell. The currentsflowing through photo cell P are directed to an amplifier A whereamplification takes place. Likewise the currents flow from the photoeel] P due to the influence of the lieht v1,eeo,335

from source M when the same has been moved across guide strip D to sucha position that its light is directed upon the shaded portion S of thelight sensitive film or strip B are directed to the ampliiier A" wherethey are amplilied. One terminal of each amplifier is preferablyconnected together and a connection between this common point and amagnetically controlled rheostat F provided with actuating coils H and Hat the coininon point on said coils is made.

The other terminals oit the amplifiers A and A are connected to the freeend ot coils H and H respectively. it is thus :ren that if the currentstrength from each pliier is the same, the currents iliiiwing Jrein thewindings H and H will be ci' equal intensity and there will be nomovement of the armature Gef the magnetically controlled rheostat.However, it the current strength produced. by the incoming signal.energy to lie'ht the source M produces less intensity upon the photocell P than the source M produces upon the photo cell P, it is readilyseen that the armature G will be drawn toward the winding H.

Associated with the receiver and amplilier A is a circuit in which thegrid b. be controlled automatically by in light intensity of. M overtha.J which variations may be producer con'nnonly known characteristicsot or other known effects. For any such tion, the sensitivity of the:.nn )liily t., teni A must creased and, therefore, upon fading cond onstaking place, the arma.w ture G will be drawn toward the winding H insuch a fashion as to decrease the amount of resistance F in the gridbias control circuit which comprises the resistance F (forming a part ofthe nui-rjnetically coin trolled rneostat), the battery L and the gridcircuits of certain tubes in the ampliiier system A. Since the externalinfluences or fading, static and all other disturbances commonly knownas strays, Y

ids, etc. ydo not usually occur with rapidity than the time required forsource M 'to traverse the recording strip B, it is suiiicient, in orderto obtain a finished picture et' unitaria inten-- sity, to regulate thesensitivity of the i ceiving system at each stroke ot the li` source Macross the hlm B. However, it is also within the scope of this inventionte control the sensitivity et the sj ste means of the shaded area S oneach edge o'i' the recoro` strip B, and such forni ei invention will besubstantial duplication o the eleinen s herein set iorth for a c .7 darea on one edge oi' the rccornnig sh; strip.

This system might also be controller. then by an operator to adjust theeener-.licences or the system in accordance with the current le@ oivingthrough the shaded portion S of the f picture stiip. This arrangementoffers the merit that the regula-ting actions are more frequent sothatcompensation is aliected more rapidly than the one before described.Y

vTo be sure, special change-over means are required in order that duringthe time S only the sensitiveness is regulated, Whereas during the `restof the time the picture istransmitted. y

By 2,- a modified formy of arrange-v nient is shown.l This arrangementis substantially like the arrangement `shown by Fig. l in that, signalsai'e received upon the antenna N and passed through ythe receiver andamplifier A where they are used tov control intensity of a lightv sourceM for the purpose of producing a record upon a record strip yB carriedby the druinB. In parallel relation to the youtputiterminalsa, (i of thereceiver and amplilier A or, Vas shown by Fig.` 2, in parallel to theinput terniinals e, e or' the receiver ancL amplifier A,

a senaiate reetif ino' and am olif inft s stomk l D C 7 is inductivelycoupled. This rectiliying and amplifying system preierably consists inthe usual type of thethree electrode vtype vacuum tube for the purposeot' producing.

ance r associated With the receiver and am,

plilicr A so as to control `the grid bias on the amplifier A and thusprovide an arrangement wherein the intensity of the received signal mayregulate the sensitiveness of the picture reproducing apparatus in thedesired manner. The arrangement shown by Fig. 2 forms an integratingdevice `oi loW inertia which is capable of compensating for a large partof the intensity fluctuations.

Having thus described our invention, What We claim is :V n. l

l. The method ot eliminating intensity variations in radio picturetransmission and reception which comprises providing an arca' of shadeupon at least one edge of the picture and controlling the sensitivenessof ri-'reproducing apparatus by the. intensity of reception on said areaof shade vat each line of the picture.

2. In an apparatus sio'nand reception, means for receiving and visiblyrecording messages, and light sensifor eliminating intenf siiyfluctuations in radio picture transmistivemeans for automaticallycontrolling the sensitivity of the receiving means in proportion to themean intensity of signal re'v c ception at any given time period.

l 3. An apparatus for eliminating intensity fluctuations in radioypicture vtransmission and reception, comprising, means for receivingsignals, means for recording messages in` accordance With saidpreceivedsignals, meanstor automatically controlling the sensitivity of `'saidpicture receiving apparatus in proportion to the mean intensity ofsignal reception at any `given "instant, said means including a Vlightsensitive means for controlling the grid blason said receivingapparatus. n y 4l. An apparatus for eliminating intensityV fluctuationsin radio ti'ansinission and rc-V ception systems, comprising, lightresponsive means' or automatically determining the meanfi'ntensity ofreception at predetermined time intervals, and meansv for controllingtheA sensitiveness of the receiving system Ain pro-portion tothedeviations in the moan intensity at said,predetermined time intervalsfrom a predeterminednormal intensity of reception.V

5. A system cluding, means for producing light intensities of a valuegoverned in accordance With the intensity of reception atv any giveniiistant, means for periodicallycomparingthe said light intensityproduced with a constant predetermined normal light intensity value,

and means controlled byvariations in said. lirst named light intensityproduced from for receiving `facsimile, Vinsaid predetermined normalvalue oi' light in- Vtensity for controlling the sensitiveness ol thesaid receiving system.

6. An apparatus vfor eliminating intensity fluctuations in radiotransmission aiidreception systems comprising,

means for comparing the intensity of reception Y at said chosen timeintervals with a normal standard of reception, and means for controllingthe sensitivenessof the receiving system in proportion to the variationsin the mean intensity of reception vfromv said predetermined normalstandardY value.:

7. A system for receiving-'facsimile .including, meansy for receivingsignals and producing vtherefroi'ii light intensitiesjoiE la valuegoverned lin accordance `with the intensityfofA reception of any giveninstant, means for periodically comparing the said light intensityproduced With a predetermined normal constant light intensity value, vand means controlled by variations in said first named light intensityproduced fromv said normal value for applying a controlling bias tosaidreceiving meansV for governing thesensitiveness'of the saidAreceiving system.

a light controlledv means for determining the intensity or' re-r ceptionat predetermined time intervals,

lio

8. The method oit eliminating intensity fluctuations in radio picturetransmission and recelition systems, Which comprises, providing an areaof shade upon at least one edge of the picture, directing a light beamgoverned in intensity by the strength of incoming signals throi'lgh theshaded area at the receiver, providmg a second shaded. area of likedensity, directing a light beam ot intensity equal to 'the normal lightintensity on the tirst shaded area through said second area, comparingthe light intensity passing through the second shaded area with thatthrough the first shaded area, and controlling the sensitiveness of areceiving apparatus in accordance with differences in the amount oflight passed through each oit said areas.

t). The method ot controlling the sensitiven'ess ol.: radio acsin'iilereceiving systems which includes, ce itrolling a light source byreceived signal pulses, directing the light produced through a shadedarea of predetermined density, periodically illuminating a light sourceet intensity corresl'ionding to normal intensity oli said lirst lightsource, directing the oght beams issuing through said second lightsource through a shaded area of like density to said lirst shaded area,comparing the amount el light passed through each of said shaded areasfrom both of said sources, and controlling the sensitiveness ol thereceiving` syst-em in accorilance with variations in the intensities oitythe said lights passed througli each of said areas.

l0. In a picture receiving system, a light source, an amplilier, meansassociated with said amplifier for Aillumunitmg said light source andproducing an intensity ol illumination. therein proportional to thestrength of incoming signals, means or periodically illuminating asource of constant light intensity, `leans for comparing the relative l.intensities ot each ot said light sources, and

moans governial by the variations in light ii'itensity oit said lirstsource ot said constant source for applying a compensating biaspotential upon said amplifier, whereby the strength et the receivedsignzns is controlled in proportion to the conditions of reception atany given i stant.

ll. In a picture receiving system, a light source, an ainpli'lier, meansa sociated with said amplifier lor illuminating said light source fromthat of said constant source for applying a compensating biasingpotential upon said ampliiier, whereby the strength et' the receivedsignals is controlled in proportion to the strength of reception at anygiven instant;

l2. ln a system for receiving pictures and the like, a receiving andamplitying means for receiving signals :trom a distant point, a lightsource, means associated with said receiver' and amplilier forilluminating said light source and producing light intensities therefromgoverned in accordance with the strength ot said received signals, alight sensitive surface tor producing pictures having their densitycontrolled by the varying intensities of light shiiiing hercon, a shadedarea on one edge oit said light seni-sitire surface, i means tordirecting said variable strength light through said shaded area, a photocell sensitive to 'the light projected through said shaded area, asource ot constant lignt intensity, a second shaded area, ot likedensity to said first sha-fled area, means lor directing the lightissuing vfrom said constant source through said secoiui shaded area, asecond photo cell, and means lier subjecting said photo cell. to saidlight Missing through said second shaded area, means tor coniparing therelative intensities of each ot said light sources by the currentsproduced thereby through said photo ci i, and means controlled byvariations in current flow through each ot said photo cells for applyinga variable controlling bias potential to said receiver', whereby saidirst inlined source oit' light intensity is controlled in accordancewith the strength oiE vthe received signals at any instant.

13. In a signalling apparatus, means for receiving and recording signalsas picture messages thereof, means determining the average intensitysignal reception at predetermined time intervals, means for comparingthe intensity ot reception at said chosen time intervals with apredetermined optimum intensity et re option, and means responsive tovariations of said received intensities 'trom said optimum intensity forvarying the sensitivity et the said receiving means to receive signals.

ll. In a signalling system ttor receiving facsimile messages, means tortranslatia,- said received signals into light intensities of valuesproportional to the average intensityo't reception at predetermined timeintervals, means for comparing 'the light intensities produced with aconstant predetermined normal light intensity value, and meansresponsive to differences in said light intensity values for controllingthe sensitivity o'l the receiving means.

1:1 In a signalling system for receiving picture messages, means forproducing light at predetermined time intervals oit an intensityproportional t the intensity of the received signals, means forcomparing the' intensity of the light produced With a constantpredetermined normal lightintensity value, and means responsive todifferences in said light intensity values for varying'the bias on thereceiving means in accordance With the intensity of signal reception atsaid y predetermined time intervals.

16. An apparatus for eliminating intensity fluctuations in radioreception systems comprising means for receiving signals, means 'l'oramplifying said received signals, means for converting said amplifiedsignal energy into proportionate light intensities for re-k cordmgpurposes, and means for controllingtlie amplification of said signalsover predetermined periods of time in accordance Vwith the intensity ofreception during 'a relatively small portion of said predetermined timeperiod.

17. An apparatus for eliminating intensity `liuctuations in receivingsystems comprising means for receiving signals, means fory recordingmessages in accordance with said received signals, and means forautomatically controiling the sensitivity of said signal recording meansin accordance with the strength of signals received during predeterminedperiods of ltime separating successive recording actions.

18. An apparatus for eliminating intensity luctuationsin radio receptionsystems comprising means 'for receiving signals, means for convertingreceived signals into light impulses of intensities proportionate 'tothe received signals, and means for periodically controlling thereceived 'signal energyin accordance With the intensity vthereof asreceived over time periods substantially less` than the time period forWhich the controlk is to be effective. y

OTTO rvoN BRONK. HANS RUKOP. Y

